add 'micrometer-core' as transitive dependency

[chickenlj]

<dependency>
      <groupId>io.micrometer</groupId>
      <artifactId>micrometer-core</artifactId>
    </dependency>

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 2.19%. Comparing base (ef6e8bd) to head (82fcca5).
Report is 56 commits behind head on 3.3.

Additional details and impacted files

@@              Coverage Diff              @@
##              3.3    #14872        +/-   ##
=============================================
- Coverage   37.53%     2.19%    -35.34%     
=============================================
  Files        1813     26083     +24270     
  Lines       80737   1389674   +1308937     
  Branches    12005    220210    +208205     
=============================================
+ Hits        30304     30559       +255     
- Misses      46042   1354671   +1308629     
- Partials     4391      4444        +53     

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[songxiaosheng]

why add it